On a multicopter, the motors must be able to vary their speed very quickly in order to maintain stability, it's the only thing keeping it level.

However some of the full size VTOL seem to manage.

It seems it's less of a problem if you have just one engine...

In this case the airflow from the propeller over the control surfaces is enough to stabilise the plane, the engine doesn't have to vary it's speed very much because the airflow is then controlled by the flaps.

There have been a few multicopters that use flaps to control airflow, but mostly for yaw control and just directing the flow not restricting/opening it.
I think there are a few projects that use flaps on all motors.

Another way would be to have variable pitch blades like on helis, but that adds a lot of mechanical complexity.

In this case the airflow from the propeller over the control surfaces is enough to stabilise the plane, the engine doesn't have to vary its speed very much because the airflow is then controlled by the flaps.

I know I know - that's the beauty of such a setup - you get something that can hover and performs like a normal plane too

Been thinking of building an RC plane for a long time... obviously of something less ambitious than what's discussed here
It would probably be best to get something like this:
[youtube]http://www.youtube.com/watch?v=oH85TNw8F20[/youtube]

the only problem is buying the right stuff (and hiding it from my family lol I feel as if I was 13 again)

Mmmm, raspberry pi A couple of my friends have got them, nearly got one myself but then thought I have enough random projects going on !

Well I have flown my phone about on the tricopter and I have unlimited data, Skype FPV ? I'm sure one could use android phone as a host to an arduino and also control it through the mobile data connection.

I might try hovering it via IP streaming on an ad-hoc network, the framerate and picture quality are good but there is still noticeable lag, probably too much for something that is only gyrostabilised.

Apparently this thing is intended to fly for 40min with a max weight of 2.5kg and is designed for "hover and stare" & "perch and stare".
Replace "hover and stare" with hover and lob paint and that would be more like it for a paintball-copter

Combine that with Jack's RC gunship video and paintball would become much more of a 3D game